3:1 rule for multi-mic setups
Check whether your microphone spacing avoids audible comb filtering from leakage.
m
m
- Distance ratio
- 3.33333: 1
- Level of the other mic (free field)
- -10.4576dB
Meets the 3:1 rule: leakage into the other microphone is at least ≈9.5 dB below the direct signal, so comb filtering stays mild.
How it works
If the second microphone is at least three times as far from a source as the first, the leakage is about 9.5 dB lower (free field). That is usually enough to keep comb filtering below audibility when the microphones are mixed together.
Formulas
- Level difference = 20 · log₁₀(d_far / d_near)
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